Nowadays the development of the technology changes with each passing day. Several kinds of lightweight or handy-sized antennas have been developed and applied to the handheld electronic device or the wireless transmission device, which are more handy-sized with each passing day; for instance, the handheld electronic device is a mobile phone or a notebook computer, and the wireless transmission device is an access point, a wireless network card or a wireless card bus. For instance, the existing planar inverted F antenna (PIFA) or the existing monopole antenna has a handy-sized structure and a satisfactory transmission performance, can be easily disposed on the inner wall of the handheld electronic device, and is widely applied in wireless transmission devices of handheld electronic devices, notebook computers or wireless communication devices. In the prior art, the innermost conductor layer and the peripheral conductor layer of the coaxial cable are respectively welded to the signal feed terminal and the signal grounding terminal of the PIFA so as to output the desired transmission signal through the PIFA. In the prior art, a PIFA capable to be applied to a multi-frequency system has properties including a complex structure and uneasy adjustments to the respective frequency bands.
The issued TW patent with No. I351,787 discloses a triple band antenna in the prior art. The issued TW patent with No. I333,715 discloses a miniaturized triple-band diamond coplanar waveguide antenna in the prior art. The issued US patent with U.S. Pat. No. 7,256,743 B2 discloses an internal multi-band antenna in the prior art. The issued US patent with U.S. Pat. No. 7,242,352 B2 discloses a multi-band or wide-band antenna in the prior art.